1. Field of the Invention
This invention relates to a composition and a method for producing a tissue simulating gel. More specifically, the invention is a simulated soft human or animal tissue particularly applicable in the field of medical research because it will not melt at elevated temperatures, it is non-hardening and non-drying for extended periods of time, and it will not support bacterial growth.
2. Description of the Prior Art
Many formulae currently exist for producing tissue simulating gels. A number of these formulae are based on agars, simple hydrated collagen gels, or polyacrylamides. These formulae often suffer from deficiencies which make them ill-suited for extended medical research: hydrated gels tend to dry out; some gels melt at the elevated temperatures involved in research; others become hosts for micro-organisms; some are too expensive or too difficult to make to be of practical value.
Using a plasticizing agent such as ethylene glycol and a coagulating or precipitating agent such as formaldehyde in preparing a substance which gives the appearance of flesh was described in U.S. Pat. No. 2,124,767 (Dawn). The invention disclosed in Dawn pertains primarily to the preparation of a masking substance used to disguise or change the appearance of an individual, particularly for acting purposes. The simulated flesh developed in Dawn is substantially dehydrated: it is prepared using ethylene glycol and water in proportions of approximately 2 to 1 respectively, following which the water is condensed out of the formulation using a pressure cooker. Dawn uses approximately 30 percent by weight of gelatin and less than 1 percent by weight of formaldehyde. One of the advantages of the Dawn formulation is its ability to withstand the heat of stage lights, though the formulation will melt and can be molded to an individual's skin using hot water.
Aside from appearance, the substance disclosed in Dawn has no other characteristics of human flesh, and it is therefore inappropriate for medical research. Unlike actual tissue, which is substantially water, the Dawn formulation after processing is substantially dehydrated. Furthermore, the Dawn formulation does not have the electrically conducting characteristic of actual tissue, nor does it have the sound conducting and wave scattering properties of actual tissue. Its ability to be melted with hot water while being molded to an individual's skin indicates it will not withstand the temperatures frequently encountered in hyperthermia research. Furthermore, because the Dawn formulation is produced using a pressure cooker, it is impractical to inject material into the substance to alter its properties before the substance sets. Once the substance has set, injection of any material will cause tearing.